An inkjet printer will produce the best quality when the environment in the region of the ejection nozzle is consistent from one jetting event to the next. Consistent temperature at the start of a jetting is one of the key environmental factors to control in order to produce the best print quality. Consequently, a robust temperature control method is a desirable element in printhead design.
In order to keep costs low, temperature sensors for an inkjet printhead must occupy a minimum layout space on the inkjet printhead IC. One type of sensor produces an output current that is proportional to the temperature on the printhead IC. One tradeoff in the design of this type of sensor is that the space may be minimized if the offset current is allowed to vary from sensor to sensor while the temperature slope is constrained to a constant value for all sensors. The offset current may be sensed at some reference temperature and the value stored by some form of memory. The sensors temperature may then be calculated by using the sensor's present current, the stored offset current, and the temperature slope to determine the temperature of the printhead IC in the vicinity of the temperature sensor.